What is the differential diagnosis and management approach for a patient presenting with upper abdominal pain?

Upper Abdominal Pain: Differential Diagnosis and Management

Immediate Life-Threatening Conditions to Exclude First

Before considering common causes, immediately rule out life-threatening conditions including mesenteric ischemia, perforated viscus, leaking abdominal aortic aneurysm, acute myocardial infarction, and ectopic pregnancy in women of reproductive age. 1, 2

Critical Initial Steps

• Obtain a pregnancy test in ALL women of reproductive age before any imaging studies to avoid unnecessary radiation exposure and prevent missing ectopic pregnancy 3, 4, 5
• Assess vital signs immediately for signs of shock (tachycardia, tachypnea, cool extremities, oliguria) which may indicate perforation, ischemia, or hemorrhage 1
• Perform digital rectal examination to detect blood or masses suggestive of malignancy 1

Differential Diagnosis by Location

Right Upper Quadrant Pain

• Biliary pathology (cholecystitis, cholelithiasis) - most common cause 5
• Hepatic pathology (hepatitis, abscess, hepatomegaly) 3, 4
• Duodenal ulcer 1, 6
• Pancreatitis (head of pancreas) 1
• Renal pathology (nephrolithiasis, pyelonephritis) 3, 4

Epigastric Pain

• Acute pancreatitis - diagnosed by serum amylase ≥4× normal or lipase ≥2× upper limit of normal 1
• Peptic ulcer disease (gastric or duodenal) 6
• Gastritis/duodenitis 1
• Acute myocardial infarction (referred pain) 2

Left Upper Quadrant Pain

• Splenic pathology (infarction, abscess, hematoma, rupture) 3, 2
• Chronic pancreatitis (tail of pancreas) - most common pancreatic cause 3
• Gastric conditions 3
• Nephrolithiasis 3
• Colonic disorders (diverticulitis, though more common in left lower quadrant) 1, 3

Diagnostic Algorithm

First-Line Laboratory Tests (Order for ALL Patients)

• Complete blood count (CBC) - assess for leukocytosis, anemia 1, 3, 4
• Comprehensive metabolic panel - evaluate electrolytes, renal function, liver function 1, 3, 4
• Pancreatic enzymes (amylase AND lipase) - lipase has higher specificity and remains elevated longer than amylase 1, 3, 4
• Urinalysis - evaluate for renal stones or infection 3, 5
• Pregnancy test (all reproductive-age females) 3, 4, 5
• Coagulation profile if surgery potentially needed 1

Critical caveat: Normal laboratory values do NOT exclude serious pathology; imaging may still be necessary based on clinical presentation 3

Imaging Strategy

Initial Imaging Choice

For adults (non-pregnant): CT abdomen/pelvis with IV contrast is first-line when diagnosis is unclear or alarm features present 1, 3

• Changes leading diagnosis in up to 51% of patients and management in 25-42% of cases 1
• Sensitivity and specificity superior to other modalities for detecting acute pathology 1
• Essential for detecting mesenteric ischemia - reduced segmental bowel-wall enhancement is 100% specific for segmental bowel infarction 1

For young patients/adolescents: Ultrasonography is first-line 4, 5

• Highest appropriateness rating (9/9) per ACR Appropriateness Criteria 5
• No radiation exposure 4, 5
• Excellent for evaluating gallbladder pathology, liver abnormalities, pancreatic conditions, splenic pathology, and renal abnormalities 3, 4, 5

Plain Radiography (Chest and Abdominal X-rays)

• Perform routinely to establish baseline and exclude perforation or obstruction 1
• Limited diagnostic value for specific upper abdominal pathology - findings are non-specific 1, 4
• May detect pneumoperitoneum, bowel obstruction, or rarely retroperitoneal gas indicating infection 1

Second-Line Imaging

• MRI without and with contrast if CT non-diagnostic and symptoms persist 1, 3, 4
  • Accuracy of 99% for acute abdominal pain in some studies 1
  • Preferred in pregnancy when US is non-diagnostic 1
  • Can be performed in <10 minutes with tailored protocols 1
• Cholescintigraphy (HIDA scan) if gallbladder disease suspected after ultrasound 5

Management Approach by Severity

Acute Pancreatitis Specific Management

Three overlapping phases: 1

1. Diagnosis and severity assessment - use serum amylase ≥4× normal or lipase ≥2× normal 1
2. Management according to severity with ongoing monitoring
3. Detection and management of complications - particularly infected necrosis

• Overall mortality should be <10%, and <30% in severe disease 1
• Sterile necrosis: 0-11% mortality 1
• Infected necrosis: 40% average mortality (range 10-70% depending on center expertise) 1

Supportive Treatment (Initiate Immediately)

• Intravenous crystalloid resuscitation 1
• Anti-emetics 1
• Bowel rest 1

Common Diagnostic Pitfalls to Avoid

• Failing to obtain pregnancy test before imaging leads to unnecessary radiation and missed ectopic pregnancy 3, 4, 5
• Relying solely on clinical findings for pancreatitis diagnosis - unreliable without biochemical confirmation 1
• Using CT as first-line in young patients unnecessarily exposes them to radiation when ultrasound is appropriate 4, 5
• Assuming normal labs exclude pathology - imaging still necessary based on clinical suspicion 3
• Repeat CT after negative initial CT has low diagnostic yield (drops to 5.9% by fourth CT); consider clinical factors like leukocytosis before repeating 1
• CT in patients with abdominal pain plus diarrhea changes management in only 11% versus 53% with pain alone - use thoughtful approach 1
• Missing pancreaticobiliary inflammatory processes, gastritis, and duodenitis - CT has relatively low negative predictive value (64%) for these conditions 1

When Diagnosis Remains Unclear

• Consider functional disorders only after organic pathology confidently excluded 3
• Avoid repetitive testing once functional pain diagnosis established 3
• CT obtained for all patients regardless of clinical suspicion increases costs without improving outcomes - obtain when clinically indicated 1